Isolation and Characterization of Proteins Interacting with Activin Type II Receptors1

Regulation of the number of activin receptors that are present in the cell membrane plays a key role in the modulation of cellular responses to activin. In order to find the regulators, a novel protein ARIPzip, interacting with activin type II receptors, was searched and identified by using yeast two-hybrid screening. ARIPzip is a splicing variant of ARIP2. This has been discussed previously. ARIPzip can specifically interact with ActR II A, and is widely distributed in mouse tissues. Overexpression of ARIPzip can cause the activin-induced transcriptional activities to increase in a dose-dependent manner while the overexpression of ARIP2 can decrease these activities. These data suggest that the C-terminal regions of ARIP2 and ARIPzip are involved in the regulation of activin signaling.